To provide an electrical junction box which can improve workability and can be attached easily without damage.

A recessed part 21, through which a wiring harness 14 is introduced, is formed in a left side wall 20 of a cover 16. Positioning guides 25 and 26 are formed on a right side wall 22 opposite to the left side wall 20. Attachment guides 27 and 28 are formed on both front and rear side walls 17 and 18 perpendicular to the left side wall 20. The positioning guides 25 and 26 attach the cover 16 slantly to a main case 11, while the positioning guides 25 and 26 are guided by both corners 11c and 11d of the main case 11, so as to make respective engagement holes 19a-19d of the cover 16 engaged successively with respective engagement members 15a-15d along a laying direction of the wiring harness 14.